Common Stock Issuance Common Stock Issuance - Additional Information - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Dec. 06, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsidiary, Sale of Stock [Line Items]
Proceeds from public offering of common stock	$ 70,500	$ 70,501	$ 0	$ 0
Common stock issued, price per share	$ 28.25
Public Offering [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock issued, shares	2,645,000
Over-Allotment Option [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock issued, shares	345,000
Common Stock [Member]
Subsidiary, Sale of Stock [Line Items]
Stock issued during period, new issues, value	$ 13,200
Additional Paid-in Capital [Member]
Subsidiary, Sale of Stock [Line Items]
Stock issued during period, new issues, value	$ 57,300